1. Field of the Invention
The present invention is related to a sustained release pheromone formation to be used in a so-called mating disruption method, that is, a method for controlling pest insects by releasing the sex pheromone of the pest insects over the field, thereby disrupting their mating.
2. Description of the Related Art
Controlling pest insects by disruption of mating is carried out by releasing the artificially synthesized sex pheromone of the target pest insects in the air and disturbing the communication between males and females to decrease a mating ratio, thereby controlling the appearance of the next generation. The sustained release formation of a sex pheromone is required to have a performance permitting the stable release of the sex pheromone during the generation stage of pest insects. The release of sustained release pheromone formation is controlled at a predetermined rate for a long time by putting the formation with one or more components of the sex pheromone or geometric isomer thereof in a plastic container and then permeating the mixture through the plastic film of the container.
The sex pheromone of pest insects such as Chilo suppressalis, Helicoverpa assulata and Helicoverpa armigera is an aliphatic aldehyde compound having 10 to 18 carbon atoms. Using the above-described sustained release formation, the release rate decreases because the aldehyde compounds easily undergo degradation such as oxidation, polymerization or the like. As a countermeasure against it, a stabilizer such as antioxidant or polymerization inhibitor is added. The antioxidant or polymerization inhibitor is effective for stabilizing the liquid of the formation in a plastic container, but exhibits no effects for the aldehyde compound once permeated from the container. The aldehyde compound permeated from the container undergoes polymerization reaction on the outer surface of the container and forms a polymer layer, which markedly decreases the release rate of the aldehyde compound from the container. It is therefore necessary to install the sustained release formations plural times during the control term of pest insects, which inevitably increases the application labor.
As a solution to these problems, the present invention has been completed. An object of the present invention is to provide a sustained release pheromone formation comprising an aldehyde compound, which formation is capable of preventing the degradation of the aldehyde compound, thereby releasing the aldehyde compound at an uniformed rate during the control term of pest insects.
The sustained release pheromone formation of the present invention which has been completed with a view to attaining the above-described object is obtained by filling, in a plastic container, a liquid mixture of a sex pheromone which is in the liquid form and is a C10-18 aldehyde and an aliphatic derivative of which number of carbon atoms is equal to or less than that of the aldehyde.
To sustained release pheromone formation according to the present invention is applicable to the disruption of mating of any insects that have at least a sex pheromone which is a C10-18 aldehyde. Examples of the insects to which the sustained release pheromone formation of the present invention is applicable include Chilo, Choristoneura, Helicoverpa, Heliothis, Parapediasia, Plutella and Platyptilia genera. The formation is particularly useful for the control of Chilo suppressalis, Choristoneura fumiferana, Helicoverpa assulta, Helicoverpa armigera, Heliothis virescens, Heliothis zea, Parapediasia teterrella, Plutella xylostella and Platyptilia carduidactyla. 
The present invention can be carried out suitably by using, as the aliphatic derivative, an aliphatic acetate of which number of carbon atoms is less than that of the aldehyde by 2 to 4, an aliphatic alcohol of which number of carbon atoms is less than that of the aldehyde by 2 to 6 or an aliphatic carboxylate ester of which number of carbon atoms is equal to or less than that of the aldehyde by 1 to 4. Since each of the above-described aliphatic derivatives has physical properties, such as film permeability and vapor pressure, similar to the aldehyde, it is released and evaporated from the formation together with the aldehyde, which prevents the retention of the aldehyde on the surface of the formation. In addition, the aliphatic derivative prevents the degradataion of the aldehyde, because it is mixed at a proper concentration in the formation.
As the aliphatic derivative, usable is one or more than one aliphatic derivatives selected from the following (i) to (iii):
(i) an aliphatic acetate of which number of carbon atoms is less than that of the sex pheromone substance by 2 to 4,
(ii) an aliphatic alcohol of which number of carbon atoms is less than that of the sex pheromone substance by 2 to 6, and
(iii) an aliphatic carboxylate ester of which number of carbon atoms is equal or less than that of the sex pheromone substance by 1 to 4.
Examples of the aliphatic acetate of which number of carbon atoms is less than that of the sex pheromone substance by 2 to 4 include aliphatic acetates having a linear, branched or cyclic alkyl or alkylene group having 6 to 16 carbon atoms, particularly 10 to 16 carbon atoms. Among them, the aliphatic acetates having a linear alkyl or alkylene group are preferred.
Examples of the linear, branched or cyclic alkyl group having 6 to 16 carbon atoms include hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, methylpentyl, methylhexyl, methylheptyl, methyloctyl, methylnonyl, methyldecyl, methylundecyl, methyldodecyl, methyltridecyl, methyltetradecyl, methylpentadecyl, ethylbutyl, ethylpentyl, ethylheptyl, ethyloctyl, ethylnonyl, ethyldecyl, ethylundecyl, ethyldodecyl, ethyltridecyl, ethyltetradecyl, dimethylbutyl, dimethylpentyl, dimethylheptyl, deimthyloctyl, dimethylnonyl, dimethyldecyl, dimethylundecyl, dimethyldodecyl, dimethyltridecyl, dimethyltetradecyl, propylpentyl, propylhexyl, propylheptyl, propyloctyl, propylnonyl, propyldecyl, propylundecyl, propyltridecyl, ethylmethylpentyl, ethylmethylhexyl, ethylmethylheptyl, ethylmethyloctyl, ethylmethylnonyl, ethylmethyldecyl, ethylmethylundecyl, ethylmethyldodecyl, ethylmethyltridecyl, diethylpentyl, diethylhexyl, diethylheptyl, diethylnonyl, diethyldecyl, diethylundecyl, diethyldodecyl and cyclohexadecyl groups.
Examples of the linear, branched or cyclic alkylene group having 6 to 16 carbon atoms include hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, methylpentenyl, methylhexenyl, methylheptenyl, methyloctenyl, methylnonenyl, methyldecenyl, methylundecenyl, methyldodecenyl, methyltridecenyl, methyletetradenecyl, methylpentadecenyl, ethylbutenyl, ethylpentenyl, ethylheptenyl, ethyloctenyl, ethylnonenyl, ethyldecenyl, ethylundecenyl, ethyldodecenyl, ethyltridecenyl, ethyltetradecenyl, dimethylbutenyl, dimethylpentenyl, dimethylheptenyl, dimethyloctenyl, dimethylnonenyl, dimethyldecenyl, dimethylundecenyl, dimethyldodecenyl, dimethyltridecenyl, dimethyltetradecenyl, propylpentenyl, propylhexenyl, propylheptenyl, propyloctenyl, propylnonenyl, propyldecenyl, popylundecenyl, propyltridecenyl, ethylmethylpentenyl, ethylmethylhexenyl, ethylmethylheptenyl, ethylmethyloctenyl, ethylmethylnonenyl, ethylmethyldecenyl, ethylmethylundecenyl, ethyl methyldodecenyl, ethyl methyltridecenyl, diethylnonenyl, diethyldecenyl, diethylundecenyl, diethyldodecenyl, hexadienyl, heptadienyl, octadienyl, nonadienyl, decadienyl, undecadienyl, dodecadienyl, tridecadienyl, tetradecadienyl, pentadecadienyl, hexadecadienyl, methylpentadienyl, methylhexadienyl, methylheptadienyl, methyloctadienyl, methylnonadienyl, methyldecadienyl, methylundecadienyl, methyldodecadienyl, methyltridecadienyl, methyltetradecadienyl, methylpentadecadienyl, ethylbutadienyl, ethylpentadienyl, ethylheptadienyl, ethylocatadienyl, ethylnonadienyl, ethyldecadienyl, ethylundecadienyl, ethyldodecadienyl, ethyltridecadienyl, ethyletradecadienyl, dimethylbutadienyl, dimethylpentadienyl, dimethylheptadienyl, dimethylocatadienyl, dimethylnonadienyl, dimethyldecadienyl, dimethylundecadienyl, dimethyldodecadienyl, dimethyltridecadienyl, dimethyltetradecadienyl, propylpentadienyl, propylhexadienyl, propylheptadienyl, propyloctadienyl, propylnonadienyl, propyldecadienyl, propylundecadienyl, propyltridecadienyl, ethylmethylpentadienyl, ethylmethylhexadienyl, ethylmethylheptadienyl, ethylmethyloctadienyl, ethylmethylnonadienyl, ethylmethyldecadienyl, ethylmethylundecadienyl, ethylmethyldodecadienyl, ethylmethyltridecadienyl, diethylpentadienyl, diethylhexadienyl, diethylheptadienyl, diethylnonadienyl, diethyldecadienyl, diethylundecadienyl, dimethyldodecadienyl and cyclohexadienyl groups.
Specific examples of the aliphatic acetate of which number of carbon atoms is less than that of the sex pheromone substance by 2 to 6 include decyl acetate, undecyl acetate, dodecyl acetate, tridecyl acetate, tetradecyl acetate, pentadecyl acetate, hexadecyl acetate, decenyl acetate, undecenyl acetate, dodecenyl acetate, tridecenyl acetate, tetradecenyl acetate, pentadecenyl acetate and hexadecenyl acetate.
Examples of the aliphatic alcohol of which number of carbon atoms is less than that of the sex pheromone substance by 2 to 6 include aliphatic alcohols having a linear, branched or cyclic alkyl or alkylene group having 4 to 16 carbon atoms, particularly 8 to 16 carbon atoms. Among them, the aliphatic alcohols having a linear alkyl or alkylene group are preferred.
Examples of the linear, branched or cyclic alkyl group having 4 to 16 carbon atoms include, in addition to the above-exemplified linear, branched or cyclic alkyl groups having 6 to 16 carbon atoms, butyl, pentyl, methylpropyl, methylbutyl, cyclobutyl and cyclopentyl groups.
Examples of the linear, branched or cyclic alkylene group having 4 to 16 carbon atoms include, in addition to the above-exemplified linear, branched or cyclic alkylene groups having 6 to 16 carbon atoms, butenyl, pentenyl, methylpropenyl, methylbutenyl, cyclobutenyl, cyclopentenyl, butadienyl, pentadienyl, methylpropadienyl, methylbutadienyl, cyclobutadienyl and cyclopentadienyl groups.
Specific examples of the aliphatic alcohol of which number of carbon atoms is less than that of the sex pheromone substance by 2 to 6 include octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, octenol, nonenol, decenol, undecenol, dodecenol, tridecenol, tetradecenol, pentadecenol and hexadecenol.
Examples of the aliphatic carboxylate ester of which number of carbon atoms is equal to or less than that of the sex pheromone substance by 1 to 4 include aliphatic carboxylate esters having a linear, branched or cyclic alkyl or alkylene group having 6 to 18 carbon atoms, particularly 10 to 18 carbon atoms. Among them, the aliphatic carboxylate esters having a linear alkyl or alkylene group are preferred.
Examples of the linear, branched or cyclic alkyl group having 6 to 18 carbon atoms include, in addition to the above-exemplified linear, branched or cyclic alkyl groups having 4 to 16 carbon atoms, heptadecyl, octadecyl, methylhexadecyl, methylheptadecyl, ethylpentadecyl, ethylhexadecyl, dimethylpentadecyl, dimethylhexadecyl, propyltetradecyl, propylpentadecyl, ethylmethyltetradecyl, ethylmethylpentadecyl, diethyltridecyl and diethyltetradecyl groups.
Examples of the linear, branched or cyclic alkylene group having 6 to 18 carbon atoms include, in addition to the above-exemplified linear, branched or cyclic alkylene groups having 4 to 16 carbon atoms, heptadecenyl, octadecenyl, methylhexadecenyl, methylheptadecenyl, ethylpentadecenyl, ethylhexadecenyl, dimethylpentadecenyl, dimethylhexadecenyl, propyltetradecenyl, propylpentadecenyl, ethylmethyltetradecenyl, ethylmethylpentadecenyl, diethyltridecenyl, diethyltetradecenyl, heptadecadienyl, octadecadienyl, methylhexadecadienyl, methylheptadecadienyl, ethylpentadecadienyl, ethylhexadecadienyl, propyltetradecadienyl, propylpentadecadienyl, ethylmethyltetradecadienyl, ethylmethylpentadecadienyl, diethyltridecadienyl and diethyltetradecadienyl groups.
Specific examples of the aliphatic carboxylate ester of which number of carbon atoms is equal to or less than that of the sex pheromone substance by 1 to 4 include methyl laurate, ethyl laurate, methyl myristate, ethyl myristate, methyl palmitate and ethyl palmitate.
Incidentally, the aliphatic derivative can be used as a combination with more than one substance selected from the above-described (i) to (iii).
Incidentally, the aliphatic derivative can be used as a combination with more than one substance selected from the above-described (i) to (iii).
When the aliphatic derivative has carbon atoms more than the above-described range, the release of the aliphatic derivative becomes inferior to that of the aldehyde, inevitably leading to the retention of the aldehyde on the outer surface of the formation and formation of a polymer layer. Moreover, the composition ratio of the aliphatic derivative in the formation increases, which dilutes the aldehyde, thereby deteriorating its release. As a result, the formation does not exhibit uniform release. The number of carbon atoms exceeding the above range is therefore not preferred.
When the aliphatic derivative has carbon atoms less than the above-described range, on the other hand, the release of the aliphatic derivative exceeds that of the aldehyde, which controls the release of the aldehyde and causes enrichment of the aldehyde, leading to the polymerization reaction. As a result, the formation does not exhibit uniform release. The number of carbon atoms less than the above range is therefore not preferred.
The present invention can be suitably carried out when the weight ratio of the sex pheromone substance to the aliphatic derivative ranges from 95:5 to 50:50, preferably 90:10 to 60:40. When the weight ratio of the sex pheromone substance is less than 50:50, the released amount of the sex pheromone substance per one formation decreases. In this case, it is necessary to increase the number of formations to be applied per unit area. When the ratio exceeds 95:5, on the other hand, the release amount of the sex pheromone substance is out of control and it retains on the outer surface of the formation and forms a polymer layer, which inevitably prevents the continuous release of the sex pheromone substance in a fixed amount.
As the sex pheromone substance, usable in the present invention is at least one aliphatic aldehyde selected from the group consisting of Z5-decenal, n-dodecanal, Z5-dodecanal, Z7-dodecenal, Z9-dodecenal, E5Z7-dodecadienal, Z5E7-dodecadienal, Z5Z7-dodecadienal, E7Z9-dodecadienal, E8E10-dodecadienal, E8Z10-dodecadienal, Z8E10-dodecadienal, E9,11-dodecadienal, Z9,11-dodecadienal, n-tetradecanal, Z5-tetradecenal, Z7-tetradecenal, Z9-tetradecenal, E11-tetradecenal, Z11-tetradecenal, E8E10-tetradecadienal, Z9E12-tetradecadienal, Z9Z11-tetradecadienal, Z9E12-tetradecadienal, E11,13-tetradecadienal, Z11,13-tetradecadienal, Z9E11,13-tetradecatrienal, Z10-pentadecenal, E9Z11-pentadecadienal, n-hexadecanal, Z7-hexadecenal, Z9-hexadecenal, E10-hexadecenal, Z10-hexadecenal, E11-hexadecenal, Z11-hexadecenal, E6Z11-hexadecadienal, Z7E11-hexadecadienal, Z7Z11-hexadecadienal, E9Z11-hexadecadienal, Z9E11-hexadecadienal, Z9E12-hexadecadienal, E10E12-hexadecadienal, E10Z12-hexadecadienal, Z10E12-hexadecadienal, E11E13-hexadecadienal, E11Z13-hexadecadienal, Z11E13-hexadecadienal, Z11Z13-hexadecadienal, E4E6Z11-hexadecatrienal, E10E12E14-hexadecatrienal, E10E12Z14-hexadecatrienal, n-octadecanal, E2-octadecanal, Z9-octadecenal, E11-octadecenal, Z11-octadecenal, E13-octadecenal, Z13-octadecenal, E14-octadecenal, E2Z13-octadecadienal, Z3Z13-octadecadienal, Z9Z12-octadecadienal, E11E14-octadecadienal, Z13Z15-octadecadienal and Z9Z12Z15-octadecatrienal.
Among them, n-tetradecanal, Z7-tetradecenal, E7-tetradecenal, Z9-tetradecenal, E9-tetradecenal, Z11-tetradecenal, E11-tetradecenal, n-hexadecanal, Z7-hexadecenal, E7-hexadecenal, Z9-hexadecenal, E9-hexadecenal, Z11-hexadecenal, E11-hexadecenal, n-octadecanal, Z9-octadecenal, E9-octadecenal, Z11-octadecenal, E11-octadecenal, Z13-octadecenal and Z13-octadecenal are particularly preferred.
The plastic container used in the present invention is made of a polyolefin polymer. Examples of the polyolefin polymer such as polyethylene, polypropylene and copolymers containing at least 90% of ethylene such as ethylene-vinyl acetate copolymer and ethylene-acrylate ester copolymer. The above-exemplified material permits the permeation of the sex pheromone substance of aliphatic compound and the release of it from the film at a proper rate.
The plastic container is in the form of a tube, capsule, ampoule or bag. Among them, the container in the tubular form is most preferred, because it permits the uniform release of the sex pheromone substance for a long time. The release at a proper rate can be maintained when the tube has an internal diameter of 0.5 to 2.0 mm, preferably 0.6 to 1.6 mm and has a wall thickness of 0.2 to 1.0 mm, preferably 0.3 to 0.8 mm.
The sustained release pheromone formation according to the present invention is thus effective for preventing the degradataion of the sex pheromone substance, whereby uniform release can be attained. The release rate can be controlled by adjusting the mixing ratio of the sex pheromone substance with the aliphatic derivative.
Production examples of the sustained release pheromone formation according to the present invention will be described below. It should however be borne in mind that the present invention is not limited to these production examples. It is possible for those skilled in the art to modify the shape or production process of the plastic container, arrangement of the sustained release formations or the like as needed depending on the field or kind of the pest insect to which the invention substance is applied.
The plastic container, more specifically, a polyethylene tube having a uniformed internal diameter and wall thickness is produced by extrusion. The sustained release formation is produced by preparing a liquid mixture wherein an aliphatic aldehyde and an aliphatic acetate have been mixed in a predetermined ratio, injecting the liquid mixture into the polyethylene tube from one end thereof, heat sealing both ends of the tube by a thermal trowel under pressure and then cutting each of the sealed portions of the tube. In the field to be subjected to pest insect control, the sustained pheromone formations are arranged at equal intervals so as to accomplish the uniform release of a necessary amount of the sex pheromone substance over the field.